Cement has been widely used in the oilfield industry where it is placed in the annular gap between casings, and between the casing and the formation wall. Cement is used because of its low cost, low permeability, and its ability to set under water. Cement is used to prevent casing corrosion, provide mechanical strength and, to provide zonal isolation where fluid communication is prevented between different zones throughout the lifetime of the well. Even when the cement sheath is initially properly set, it can be damaged by the stresses induced by downhole temperature and pressure changes, which can be caused by, for example, drilling of wellbore, perforation of casing and hydraulic fracture stimulation of reservoir. Once the cement sheath is damaged and loses its integrity, the consequences can include loss of hydrocarbon production, environmental pollution, and even catastrophic disasters. Furthermore, preventing cement failure is becoming even more important due to the increase in the number of wells operated in extreme conditions, as well as increasingly rigorous environmental regulation.